Expression Differentiation Is Constrained to Low-Expression Proteins over Ecological Timescales

Area of Science:

• Evolutionary Biology
• Molecular Evolution
• Genomics

Background:

• Protein expression level is a strong predictor of evolutionary rate, with high-expression proteins evolving slower than low-expression proteins.
• This negative correlation between expression level and evolutionary rate is observed across species over long divergence times.
• It remains unknown if this relationship applies to microevolutionary processes within a species over ecological timescales.

Purpose of the Study:

• To investigate whether rapid protein expression evolution is restricted to low-expression proteins due to constraints on high-expression proteins over ecological timescales.
• To determine if expression level influences the availability of beneficial variants under directional selection within a species.

Main Methods:

• Compared venom protein expression levels across mainland and island populations of three pit viper species.
• Analyzed protein expression differentiation over ecological timescales (<5000 years).

Main Results:

• Significant differentiation in protein expression levels was detected in two of the three pit viper species.
• Rapid expression differentiation was exclusively observed in low-expression proteins.
• High-expression proteins showed constraints limiting the availability of beneficial expression variants.

Conclusions:

• Constraints on high-expression proteins reduce the availability of beneficial variants, limiting their rapid evolution.
• Low-expression proteins can evolve more rapidly, potentially leading to faster adaptation.
• Ecological timescales may reveal different evolutionary dynamics compared to long-term patterns.